Oxydation par la réaction de Fenton modifiée des polluants organiques en présence des oxydes de fer (II, III), Fenton-like oxidation of organic pollutants in the presence of iron (II, III) oxides

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Sous la direction de Bernard Humbert, Khalil Hanna, Nansheng Deng
Thèse soutenue le 29 mai 2009: Wuhan (Chine), Nancy 1
Cette thèse avait pour but d’étudier les phénomènes physico-chimiques se produisant à l’interface solide minéral/solution en présence d’un oxydant et d’un polluant organique. L’apport du fer comme catalyseur pour l’oxydation du polluant était évalué en sélectionnant deux types d’oxydes mixtes (FeII, FeIII) de fer. Il s’agit d’interactions solide/polluant, oxydant/solide et oxydant/polluant dont les mécanismes réactionnels sont loin d’être compris. Les mécanismes d’oxydoréduction des composés organiques dans la phase aqueuse en contact avec ces minéraux sont fortement influencés par leurs propriétés de surface, leur réactivité vis-à-vis des polluants et la nature des oxydants utilisés. En effet, les phénomènes se produisant à l’interface minéral/solution pourraient avoir un impact significatif d’une part sur l’efficacité de l’oxydation et d’autre part sur la stabilité du système solide. Des caractérisations spectroscopiques couplées à des analyses chimiques ont permis à la fois de décrire les mécanismes d’oxydoréduction à l’interface solide/liquide et de suivre l’efficacité de l’oxydation ainsi que l’évolution structurale du solide. L’influence de l’oxydation sur la nature minéralogique du solide a été abordée. De même, l’effet de la présence des agents chélatants agissant comme pièges des radicaux hydroxyles libres (•OH) sur la performance de l’oxydation a été également étudié. Les résultats présentés dans ce manuscrit contribuent à la bonne compréhension des mécanismes se produisant à l’interface oxyde/solution lors de l’oxydation par Fenton modifiée. Ce travail a permis de mettre en évidence les paramètres optimums durant la dégradation d’un polluant organique comme le pentachlorophénol (PCP) dans le système magnétite/H2O2. De plus, les facteurs influençant le contact oxydant-polluant en comparant deux polluants (RhodamineB et Pentachlorophénol) et deux types d’oxydes mixtes de fer ont été déterminés. Parmi ces facteurs, on peut citer l’hydrophobicité, l’équilibre acido-basique et l’adsorptivité de la molécule, et le contenu en FeII, surface spécifique, minéralogie et propriétés de surface du solide. Il s’agit alors d’une étape significative dans l’évaluation et le suivi de la réaction d’oxydation des polluants organiques dans les sols et les eaux contaminés. L’utilisation de ces données expérimentales a permis une bonne description de la réactivité intrinsèque des oxydes de fer et aussi une optimisation de la réaction d’oxydation. L’utilisation d’un agent complexant fort du fer comme l’EDTA conduit à de meilleurs résultats en phase homogène à pH7. Cependant, l’utilisation de l’oxalate comme les cyclodextrines devient plus intéressante en phase hétérogène. Ces résultats mettent en évidence le rôle important des interactions physico-chimiques à l’interface catalyseur solide/solution dans la détermination de la performance de la réaction d’oxydation du Fenton hétérogène.
-Réaction de Fenton
Firstly, PCP was chosen as a model pollutant, to investigate the oxidation of PCP on the surface of magnetite used as heterogeneous catalyst. Oxidation experiments were carried out under various experimental conditions at neutral pH and correlated with the adsorption behavior. The surface reactivity of magnetite was evaluated by conducting the kinetic study of both H2O2 decomposition and PCP oxidation experiments. The occurrence of the optimum values of H2O2 and magnetite concentrations for the effective degradation of PCP could be explained by the scavenging reactions with H2O2 or iron oxide surface. All batch experiments indicate that Fenton-like oxidation of PCP was controlled by surface mechanism reaction and the species compete with each other for adsorption on a fixed number of surface active sites. The apparent degradation rate was dominated by the rate of intrinsic chemical reactions on the oxide surface rather than the rate of mass transfer. Raman analysis suggested that the sorbed PCP was removed from magnetite surface at the first stage of oxidation reaction. All X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Mössbauer spectroscopy and chemical analyses showed that the magnetite catalyst exhibited low iron leaching, good structural stability and no loss of performance in second reaction cycle. Secondly, Rhodamine B (RhB) was chosen as a model compound pollutant. Two types of iron (II, III) oxides were used as heterogeneous catalysts and characterized by XRD, Mössbauer spectroscopy, BET surface area, particle size and chemical analyses. The catalytic efficiency of iron (II, III) oxide to promote Fenton-like reaction was examined at neutral pH. The adsorption to the catalyst changed significantly with the pH value and the sorption isotherm was fitted using the Langmuir model for both solids. Both sorption and FTIR results indicated that surface complexation reaction may take place in the system. The variation of oxidation efficiency against H2O2 dosage and amount of exposed surface area per unit volume was evaluated and correlated with the adsorption behavior in the absence of oxidant. There is also an optimum amount of H2O2 value for the degradation of RhB. The phenomena could also be explained by the scavenging effect of hydroxyl radical by H2O2 or by iron oxide surface (like the oxidation of PCP). Sorption and decolourization rate of RhB as well as H2O2 decomposition rate were found to be depended on the surface characteristics of iron oxide. The kinetic oxidation experiments showed that structural FeII content strongly affect the reactivity towards H2O2 decomposition and therefore RhB decolourization. Finally, the effect of chelating agent on the heterogeneous Fenton reaction rate of pentachlorophenol in the presence of magnetite was investigated. Six kinds of chelating agents including oxalate, EDTA, CMCD, tartarate, citrate and succinate were chosen. The PCP oxidation rate in this system was significantly improved by using chelating agents at neutral pH. The kinetic rate constant was increased by 5.7, 4, 3.2, 2.4, 2.5 and 1.7 times with oxalate, EDTA, CMCD, tartarate, citrate and succinate, respectively. The enhancement factor of heterogeneous oxidation rate was found to be not correlated with that of dissolved iron dissolution amount. In homogeneous Fenton system (dissolved Fe2+ or Fe3+), EDTA-driven reaction showed the highest oxidation rate, while oxalate seems to be more efficiency in heterogeneous Fenton system (Fe3O4). This observation could be explained by the inactivation of iron surface sites which become unavailable for the interactions with H2O2 to initiate Fenton-like reactions. These results demonstrated that the chelating agent-promoted dissolution of magnetite did not play the key role in determining the efficiency of heterogeneous Fenton oxidation.
Source: http://www.theses.fr/2009NAN10041/document

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JOINT PhD
WUHAN UNIVERSITY AND
UNIVERSITY HENRI POINCARE

Oxydation par la réaction de Fenton modifiée des polluants
organiques en présence des oxydes de fer (II, III)

Fenton-like oxidation of organic pollutants
in the presence of iron (II, III) oxides
by
Xiaofei Xue
Speciality: Environmental Science
Ecole Doctorale Lorraine de Chimie et Physique Moléculaires
th
Date of defence: May 29 , 2009
Place of defence: Wuhan University, Wuhan city, PR CHINA.

Composition of PhD defence

M. MAILHOT G. Directeur de recherche CNRS (Université Blaise Pascal) Referee
M. CHOVELON J-M. Professeur (Université Lyon 1) Examiner
M. BAO Z. Professor (China University of Geosciences) Referee
M. WU F. A. Professor (Wuhan University) Examiner
M. DENG N. Professeur (Wuhan University) Supervisor
M. HUMBERT B. Professeur (Nancy Université) Supervisor
M. HANNA K. A. Professeur (Nancy Université) Co-Supervisor

Laboratoire de Chimie Physique et Microbiologie pour l’Environnement, LCPME UMR7564, CNRS, FRANCE and Department of
Environmental science, Wuhan University, CHINA. Résumé

Cette thèse avait pour but d’étudier les phénomènes physico-chimiques se
produisant à l’interface solide minéral/solution en présence d’un oxydant et d’un
polluant organique. L’apport du fer comme catalyseur pour l’oxydation du polluant était
II IIIévalué en sélectionnant deux types d’oxydes mixtes (Fe , Fe ) de fer. Il s’agit
d’interactions solide/polluant, oxydant/solide et oxydant/polluant dont les mécanismes
réactionnels sont loin d’être compris. Les mécanismes d’oxydoréduction des composés
organiques dans la phase aqueuse en contact avec ces minéraux sont fortement
influencés par leurs propriétés de surface, leur réactivité vis-à-vis des polluants et la
nature des oxydants utilisés. En effet, les phénomènes se produisant à l’interface
minéral/solution pourraient avoir un impact significatif d’une part sur l’efficacité de
l’oxydation et d’autre part sur la stabilité du système solide. Des caractérisations
spectroscopiques couplées à des analyses chimiques ont permis à la fois de décrire les
mécanismes d’oxydoréduction à l’interface solide/liquide et de suivre l’efficacité de
l’oxydation ainsi que l’évolution structurale du solide. L’influence de l’oxydation sur la
nature minéralogique du solide a été abordée. De même, l’effet de la présence des agents
•chélatants agissant comme pièges des radicaux hydroxyles libres ( OH) sur la
performance de l’oxydation a été également étudié.
Les résultats présentés dans ce manuscrit contribuent à la bonne compréhension des
mécanismes se produisant à l’interface oxyde/solution lors de l’oxydation par Fenton
modifiée. Ce travail a permis de mettre en évidence les paramètres optimums durant la
dégradation d’un polluant organique comme le pentachlorophénol (PCP) dans le
système magnétite/H O . De plus, les facteurs influençant le contact oxydant-polluant 2 2
en comparant deux polluants (RhodamineB et Pentachlorophénol) et deux types
d’oxydes mixtes de fer ont été déterminés. Parmi ces facteurs, on peut citer
l’hydrophobicité, l’équilibre acido-basique et l’adsorptivité de la molécule, et le contenu
IIen Fe , surface spécifique, minéralogie et propriétés de surface du solide. Il s’agit alors
d’une étape significative dans l’évaluation et le suivi de la réaction d’oxydation des
polluants organiques dans les sols et les eaux contaminés. L’utilisation de ces données
expérimentales a permis une bonne description de la réactivité intrinsèque des oxydes de
fer et aussi une optimisation de la réaction d’oxydation.
L’utilisation d’un agent complexant fort du fer comme l’EDTA conduit à de
meilleurs résultats en phase homogène à pH7. Cependant, l’utilisation de l’oxalate
comme les cyclodextrines devient plus intéressante en phase hétérogène. Ces résultats
mettent en évidence le rôle important des interactions physico-chimiques à l’interface
catalyseur solide/solution dans la détermination de la performance de la réaction
d’oxydation du Fenton hétérogène.

Abstract

2+As an advanced oxidation processe, Fenton reaction (Fenton reagent: (Fe /H O )) 2 2
is one of the most powerful oxidation used world around, which has been proved to be
a promising and attractive treatment method for the degradation of a large number of
hazardous and organic pollutant. Fenton process can generate free hydroxyl radical
•(HO ), a strong oxidant capable of reacting with practically all types of organic and
inorganic compounds. However, the classic Fenton reaction has some disadvantages
such as the Fe(III)-iron sludge was produced during the reaction and the solution
needed acidification before carrying out the reaction. To overcome these drawbacks,
many researchers focused on using modified Fenton system, the so called Fenton-like
system. In this research, iron solid mineral was used instead of soluble iron and it
offers significant advantages in separation. Since in this case, the catalyst can be easily
recovered by sedimentation or filtration and be further used.
Iron is the most abundant transition metal in natural environment. It widely exists
in soil, fresh waters, ocean and atmosphere as a kind of mineral on surface of the Earth.
Different kinds of iron oxides, such as goethite, hematite, magnetite, and ferrihydrite,
are among the most ubiquitous forms of iron species under environmental relative
conditions (pH 4-9). In this thesis, two kinds of mixed iron (II, III) oxides were chosen,
II IIIwhich have different Fe /Fe ratio, special surface area (SSA), mean particle diameter,
site density and so on. Two kinds of model pollutant (pentachlorophenol (PCP) and
Rhodamine B (RhB)) which are widely used chemicals all over the world were
selecetd. They are toxic, persistant, very resistant to biodegradation and considered as
priority organic pollutant by USEPA.
Firstly, PCP was chosen as a model pollutant, to investigate the oxidation of PCP
on the surface of magnetite used as heterogeneous catalyst. Oxidation experiments
were carried out under various experimental conditions at neutral pH and correlated
with the adsorption behavior. The surface reactivity of magnetite was evaluated by
I
conducting the kinetic study of both H O decomposition and PCP oxidation 2 2
experiments. The occurrence of the optimum values of H O and magnetite 2 2
concentrations for the effective degradation of PCP could be explained by the
scavenging reactions with H O or iron oxide surface. All batch experiments indicate 2 2
that Fenton-like oxidation of PCP was controlled by surface mechanism reaction and
the species compete with each other for adsorption on a fixed number of surface active
sites. The apparent degradation rate was dominated by the rate of intrinsic chemical
reactions on the oxide surface rather than the rate of mass transfer. Raman analysis
suggested that the sorbed PCP was removed from magnetite surface at the first stage of
oxidation reaction. All X-ray powder diffraction (XRD), X-ray photoelectron
spectroscopy (XPS), Mössbauer spectroscopy and chemical analyses showed that the
magnetite catalyst exhibited low iron leaching, good structural stability and no loss of
performance in second reaction cycle.

Secondly, Rhodamine B (RhB) was chosen as a model compound pollutant. Two
types of iron (II, III) oxides were used as heterogeneous catalysts and characterized by
XRD, Mössbauer spectroscopy, BET surface area, particle size and chemical analyses.
The catalytic efficiency of iron (II, III) oxide to promote Fenton-like reaction was
examined at neutral pH. The adsorption to the catalyst changed significantly with the
pH value and the sorption isotherm was fitted using the Langmuir model for both
solids. Both sorption and FTIR results indicated that surface complexation reaction
may take place in the system. The variation of oxidation efficiency against H O 2 2
dosage and amount of exposed surface area per unit volume was evaluated and
correlated with the adsorption behavior in the absence of oxidant. There is also an
optimum amount of H O value for the degradation of RhB. The phenomena could 2 2
also be explained by the scavenging effect of hydroxyl radical by H O or by iron oxide 2 2
surface (like the oxidation of PCP). Sorption and decolourization rate of RhB as well
as H O decomposition rate were found to be depended on the surface characteristics 2 2
IIof iron oxide. The kinetic oxidation experiments showed that structural Fe content
strongly affect the reactivity towards H O decomposition and therefore RhB 2 2
II
decolourization. The site density and sorption ability of RhB on surface may also
influence the oxidation performance in iron oxide/H O system. The iron (II, III) 2 2
oxides catalysts exhibited low iron leaching, good structural stability and no loss of
performance in second reaction cycle. The sorption on the surface of iron oxide with
catalytic oxidation using hydrogen peroxide would be an effective oxidation process
for the contaminants.

Finally, the effect of chelating agent on the heterogeneous Fenton reaction rate of
pentachlorophenol in the presence of magnetite was investigated. Six kinds of
chelating agents including oxalate, EDTA, CMCD, tartarate, citrate and succinate were
chosen. The PCP oxidation rate in this system was significantly improved by using
chelating agents at neutral pH. The kinetic rate constant was increased by 5.7, 4, 3.2,
2.4, 2.5 and 1.7 times with oxalate, EDTA, CMCD, tartarate, citrate and succinate,
respectively. The enhancement factor of heterogeneous oxidation rate was found to be
not correlated with that of dissolved iron dissolution amount. In homogeneous Fenton
2+ 3+system (dissolved Fe or Fe ), EDTA-driven reaction showed the highest oxidation
rate, while oxalate seems to be more efficiency in heterogeneous Fenton system
(Fe O ). This observation could be explained by the inactivation of iron surface sites 3 4
which become unavailable for the interactions with H O to initiate Fenton-like 2 2
reactions. Indeed, EDTA can bind more strongly than oxalate to magnetite surface and
compete more actively with H O or PCP for the sorption on the surface active sites. 2 2
These results demonstrated that the chelating agent-promoted dissolution of magnetite
did not play the key role in determining the efficiency of heterogeneous Fenton
oxidation. The surface interactions of oxidant with the catalyst surface appear to be the
rate-determining step in heterogeneous Fenton system, rather than the iron oxide
dissolution rate.



III
Acknowledgements

I would like to thank very much to my supervisor Dr. khalil Hanna. During the year in
France, he not only helped me with my work, but also gave many helps for my living.
It is my pleasure and I’m very lucky to work with him, I learned many things from him.
He helped me about the experiment, he helped me about the papers, and also he helped
me with my thesis. Without his help I can’t finish all my works in two years. Without
his support I can’t made the interuniversity program between Nancy University and
Wuhan University.

I would like to thanks my supervisor Pro.Deng Nansheng. Thanks for his guidance
during the four years study in Wuhan university, thanks for his support of the
interuniversity program between Nancy university and Wuhan university.

I would like to thanks Mr. Feng Wu, for his kindly help and guide about my
experiments during my study in Wuhan University, and also thanks for his help about
making the interuniversity program.

Special thanks for Pr. Bernard Humbert for the help of the interuniversity agreement
between Nancy University and Wuhan University.

Thanks for my friend Benoit Rusch, during the year I study in Nancy University. He
had given many help to me about my experiments. And he also gave many help to my
living in France. I’m always very happy to work together with him. And also thanks
for the kindly help from my colleague Dr. Kone Tiangoua.

Thanks for Mustapha Abdelmoula for Mössbouer analysis and for many helpful
discussions with regards to the magnetite structure, Thanks for Christelle Despas for
the help of using the HPLC. Thanks for Cedric for the help of FTIR and RAMAN.

IV
Thanks for the help of Ms. Mei Xiao and Ms.Ling Zhang for the experimental
equipment and also the other help when I was in Wuhan University.

Thanks for Mr. Guanghui Wang, he gave a lots of help to me when I was in Wuhan
university. I’m very happy to work with Dr Xu Zhang, Dr Beibei Wang, Dr Lin Deng,
Dr Yuanxiang Liu, Dr. Li Guo, Dr Lei Wang, Ms. Liu Yang and also thanks for their
help. I’m happy to be colleague with Dr. Wenyu Hang, Ms. Liwei Hou, Mr. Xuwei Wu,
Mr. Zhiping Wang, Mr. Liwei Bai.

Thanks for the fund support of China Scholarship Council (CSC) affiliated with the
Ministry of Education of the P.R.China. Thanks for choosing me and giving me this
chance. Thanks for Mr. Xiaotao Zhang who is working in the Education Service of
China Embassy in Paris France.

Finally, I would especially like to thank my family; my parents and my wife’s parents
for always being there with encouragement; I would like to thank my wife Cui, for her
love, understanding and support, I can overcome any difficulties. We have been
together since college, we work hard together to pursue the happies of life for many
years, I cannot imagine life without her.














V
Publication list

1. Xiaofei Xue, Khalil Hanna, Nansheng Deng. Fenton-like oxidation of Rhodamine B
in the presence of two types of iron (II, III) oxide.
Journal of Hazardous Materials, In Press, Available online 3 December 2008.

2. Xiaofei Xue, Khalil Hanna, Mustapha Abdelmoula, Nansheng Deng. Adsorption
and oxidation of PCP on the surface of magnetite: Kinetic experiments and
spectroscopic investigations.
Applied Catalysis B: Environmental, In Press, Available online 15 January 2009.

3. Xiaofei Xue, Khalil Hanna, Christelle Despas, Nansheng Deng. Effect of chelating
agent on the oxidation rate of PCP in the magnetite /H O system at neutral pH. 2 2
Journal of Molecular Catalysis A: Chemical, In press, 2009.

VI

CONTENTS

CHAPTER 1. INTRODUCTION ..........................................................................- 2 -
1.1 Background .............................................................................................- 2 -
1.2 Research goals and objectives..................................................................- 4 -
1.3 Organization of thesis ..............................................................................- 5 -
CHAPTER 2. LITERATURE REVIEW ................................................................- 8 -
2.1 Advanced oxidation processes (AOPs) ....................................................... - 10 -
2.2 Fenton reaction .......................................................................................... - 11 -
2.2.1 Background of Henry John Horstman Fenton....................................... - 11 -
2.2.2 Fundamental chemistry of the Fenton reaction ..................................... - 12 -
2.2.3 Mechanism of Iron-oxo iron and complexes in Fenton reaction............ - 17 -
2.2.4. Main factors of Fenton reaction........................................................... - 19 -
2.2.5 Disadvantages ...................................................................................... - 28 -
2.3 Heterogeneous Fenton-like reaction ........................................................... - 29 -
2.3.1 Iron oxides ........................................................................................... - 30 -
2.3.2 Haber-Weiss (Haber and Willstätter) reaction ...................................... - 33 -
2.4 Model pollutant.......................................................................................... - 37 -
2.4.1 Pentachlorophenol (PCP) ..................................................................... - 37 -
2.4.2 Rhodamine B (RhB)............................................................................. - 41 -
CHAPTER 3. EXPERIMENTAL MATERIAL, METHODS AND PROCEDURES ... -
46 -
3.1 Material ..................................................................................................... - 46 -
3.1.1 Iron oxides ........................................................................................... - 46 -
3.1.2 Model pollutant.................................................................................... - 46 -
3.1.3 Reagents .............................................................................................. - 47 -
3.2 Preparation of solution ............................................................................... - 48 -
3.2.1 Preparation the stock solution............................................................... - 48 -
3.2.2 Preparation of the reaction solution ...................................................... - 50 -
3.3 Reactor of the experiment .......................................................................... - 51 -
3.4.1 PCP analysis by reversed phase liquid chromatography (HPLC) .......... - 52 -
i